Once you reach the level where you can use all four turtles at once, you must begin building a relationship with your brothers. You can do this by using your brother throw, but take turns who is doing the throw. For example, Leo throws Ralph and vice versa, Don throws Mike. Successful brother throws will build their relationship, and then you can use their double team attacks. However, failed throws will make them mad at you, and they will go away and you must win their trust again. Raphael seems to be the one that you make mad most often.

Getting an "A" in working with your brothers is very simple. When you are fighting, use the turtle's special move then fight until more enemies appear. Switch turtles and do the same thing until all enemies are defeated.